1. Field of the Invention
The invention relates to a gas turbine combustion chamber in which the combustion chamber wall is cooled by means of impingement cooling.
2. Discussion of Background
Such gas turbine combustion chambers are known. In order to effect the impingement cooling concept, for example to cool an annular combustion chamber wall, a perforated plate is used which generates a cooling gas jet in such a way that it meets the surface located under it at right angles and cools the surface. The perforated plate and the impingement surface together form a duct in which the entering cooling air mass is transported further.
The heat transfer coefficient of the first cooling jet is the largest. It then decreases along the length of the impingement cooling duct because the influence of the increasing transverse flow velocity leads to increasing deflection of the impingement jet.
After a fairly long distance, therefore, the cooling effect of this impingement cooling is only slightly better than that of pure convection cooling.
In order, nevertheless, to achieve a cooling effect which is to some extent uniform over a certain distance, the impingement cooling flows have previously been respectively restarted so that an approximately saw-toothed shape around a required average value is achieved for the heat transfer coefficient.
The disadvantages of the prior art consist in the fact that no uniform cooling effect is achieved over the complete length of the cooling section and that additional complication has to be accepted for the restarting of the impingement cooling flows.
The known technical solution from the Deutsche Offenlegungsschrift 28 36 539, in which cooling air guides in the form of tubes of a constant length are inserted into the openings of the perforated plate in order to improve the impingement cooling effect in a hot gas casing for gas turbines, cannot obviate these disadvantages either.